955 resultados para 3-7-1


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Four liquid crystals (LC) 3,7a-bis(4-alkyloxyphenyl)-7,7a-dihydro-6H-isoxazolo[2,3-d][1,2,4]oxadiazol-6-yl)acetic acid (7a-d) were synthesised and the mesomorphic behaviour reported. The LCs were characterised as 2: 1 bisadducts, which were obtained from a double [3+2] 1,3-dipolar cycloaddition. In the first step, the cycloaddition of 4-alkyloxyphenylnitrile oxide (4a-d) and vinylacetic acid (5) gave the initial unobserved 1:1 cycloadducts 2-[3-(4-alkyloxyphenyl)-4,5-dihydroisoxazol-5-yl]acetic acid (6a-d). In the second step, the addition of a second equivalent of 4 to 6 yielded the 2: 1 bisadducts 7a-d without any traces of 6. All compounds 7a-d were unstable during the transition from the mesophase to the isotropic state upon first heating as evidenced by the large peaks in the differential scanning calorimetry traces. Due to the chemical instability of the compounds upon heating, the transition temperature related to the smectic C to smectic A transitions was acquired by means of an image processing method. X-Ray diffraction experiments were also used to analyse the liquid-crystalline phases. A theoretical calculation was performed using density functional theory (DFT) methods at the PBE1PBE/6-311+G(2d,p) level (with solvent effect) in order to get information about the energetic profile of the 2: 1 cycloaddition. DFT studies revealed that the cycloaddition process is controlled by the HOMO(dipolarophile) - LUMO(1,3-dipole), and that the double [3+2] 1,3-dipolar cycloaddition reaction is quite possible.

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7 Briefe zwischen Edward Mead Earle, American Committee for International Studies, Princeton N. J. und Max Horkheimer, 1940-1941; 3 Briefe zwischen Margaret Ebert und Margot von Mendelssohn, 1941, 28.08.1941; 6 Briefe zwischen C. C. Eckhardt und Max Horkheimer, 1940; 5 Briefe zwischen Kay Eckstein und Max Horkheimer, 1940; 2 Briefe zwischen George Eckstein und Max Horkheimer, 16.05.1939, 35.05.1939; 1 Brief von F. K. Eden an Max Horkheimer, 02.04.1944; 33 Briefe zwischen Leopold Eder, Frieda Eder, Ruth Eder und Max Horkheimer, 1937-1940; 2 Briefe zwischen Dale Edwards und Max Horkheimer, 16.07.1940; 1 Brief von Hedwig Ehrlich an Max Horkheimer; 1 Brief von Max Horkheimer an Albert Einstein, 20.02.1935; 1 Brief von Max Horkheimer an W. Eisemann, 02.11.1939; 1 Brief von Else Eisner an Max Horkheimer, 09.12.1935; 2 Briefe zwischen Edit Elbogen und Max Horkheimer, 24.03.1942, 26.03.1942; 1 Brief von Käte von Hirsch an Max Horkheimer, 03.08.1941; 2 Briefe von Emmy Elbogen an Margot von Mendelssohn, 1945; 2 Briefe zwischen Paul Elbogen und Max Horkheimer, 02.06.1944, 09.06.1944; 4 Briefe zwischen Norbert Elias und Max Horkheimer, 1934-1935; 1 Brief von Werner B. Ellinger an Max Horkheimer, 16.12.1937; 19 Briefe zwischen dem Emergency Committee in Aid of Displaced Foreign Scholars New York und Max Horkheimer, 1938-1944; 2 Briefe zwischen dem Emergency Rescue Committee New York und Max Horkheimer, 12.06.1941, 14.06.1941; 1 Brief von F.L. Neumann an Emhardt, 13.02.1939; 23 Briefe zwischen Alice Engel und Max Horkheimer, 1937-1941; 9 briefe zwischen Paul Doernberg, Sofie Doernberg und Max Horkheimer, 1940-1942; 3 Briefe zwischen der Hebrew Sheltering and Immigrant Aid Society New York und Max Horkheimer, 05.01.1942, 1942; 1 Brief von der Selfhelp of Emigres from Central Europe, New York an Max Horkheimer, 18.08.1941; 2 Briefe zwischen R. Weissmann und Max Horkheimer, 09.01.1941, 03.02.1941; 5 Briefe zwischen Ernst Engelberg und Max Horkheimer, 1939-1940, 07.06.1939; 1 Brief von Fritz Epstein an Max Horkheimer, 10.04.1937; 1 Brief von Erika Ermel an Max Horkheimer, 15.09.1948; 2 Briefe zwischen Max Ernst und Max Horkheimer, 23.01.1936; 4 Briefe zwischen Margot Esser und Max Horkheimer, 1935-1936; 16 Briefe zwischen Rene Etiemble und Max Horkheimer, 1936-1938; 4 Briefe zwischen L.M. Ettlinger und Max Horkheimer, 1937; 8 Briefe zwischen Walter Fabien und Max Horkheimer, 1937-1941; 1 Brief von Max Horkheimer an Henry Pratt Fairchild, 25.03.1941; 2 Briefe zwischen Marvin Farber und Max Horkheimer, 14.03.1940, 17.05.1940; 4 Briefe zwischen Walter Farley udn Max Horkheimer, 1935, 01.10.1935; 8 Briefe zwischen Alexander Farquharson und Max Horkheimer, 1935-1939;